cdTree VB Knowledge Solutions Compact Data This option will compact the data file, making it smaller in size. Invoking this action will copy the original file to cdTree.bak, and the creation of a smaller size data file called cdTree.dat. While the system is compacting the data, an animated screen will show up to inform you of the action. You can cancel the operation at any time. If the operation is interrupted during the compacting of the data, no data will be lost.